I struggle to find on topic site to ask my question. It has to do with mobile phone tethering, so here is link to my attempt to ask it on Network Engineering:
I am in US and I bought Punkt MP02, and it works on AT&T. This phone has tethering option. I just go to settings, click "Turn on Tethering" and that's it, it just works. Now, I know that US carriers charge for tethering, and you would have to go online or in store to subscribe to this feature to be available on the smartphone, and pay $30-$400 for it monthly, depending on how much MB/GB limit you want. But I did not do any of that with my Punkt. I just turned on tethering in my settings and it worked.
So, does/can AT&T know I started using tethering and will charge me for that, or the kind of tethering which is implemented in Punkt, perhaps, hardware supported, somehow, and therefore makes it impossible for AT&T to figure out I'm using tethering, hence no charges will appear on my next bill?
Edit (after this question was marked off-topic):
To clarify. I fully understand nobody has incite on how AT&T does their business. But my minimal, basic understanding of how electromagnetic waves work I suspect that it is possible to give an answer to the question of "according to laws of physics - more specifically that subset of physics which has to deal with electromagnetic waves - is it physically possible for a cellular network carrier to determine whether somebody uses tethering on their mobile device without their "approval" (aka. their subscription plan) and charge them money for that?".
Can somebody suggest me a site where this question is not off-topic?
Should I ask this on Android Enthusiasts because Punkt is running on Android? But my question is not specifically about Android, it's about the physics of tethering.
Should I ask it on Physics? Feels off topic there, too. Physics SE does not even have a tag for "tethering".